Enhanced lube oil yield by low or no hydrogen partial pressure catalytic dewaxing of paraffin wax

ABSTRACT

Catalytic dewaxing of paraffin containing feeds with a catalyst having a certain pore structure, where the feeds are preferably produced from syn gas using a non-shifting Fischer-Tropsch catalyst, is accomplished in the substantial absence of added hydrogen, and a cyclic isomerization-catalyst regeneration process is provided.

[0001] This application is a Continuation-In-Part of U.S. Ser. No.10/266,342 filed Oct. 8, 2002.

FIELD OF THE INVENTION

[0002] This invention relates to a process of catalytically dewaxingparaffin containing hydrocarbons. More particularly, this inventionrelates to the production of lube base oils and diesel range oils with apre-determined or pre-selected pour point or cloud point by catalyticdewaxing in the substantial absence of added hydrogen, at low or nohydrogen partial pressures.

BACKGROUND OF THE INVENTION

[0003] There is a need for high quality products having a relativelyhigh boiling point, such as lube base oils and diesel range oils, withlow pour and cloud points. The production of lube base oils and dieselrange oils by the hydroprocessing of paraffin containing feeds is wellknown, e.g., hydroisomerization or hydrocracking of the paraffin feed.The processes are generally catalytic and are usually carried out atrelatively high hydrogen pressures, e.g., >500 psi (3448 kPa) hydrogenpartial pressure. Catalytic dewaxing is a form of hydroprocessing andinvolves paraffin isomerization and some hydrocracking. Dewaxing ofparaffin containing feeds serves to decrease their pour and cloudpoints, mainly by isomerization of n-paraffins. Hydrocracking, however,is generally undesired in a dewaxing process, because it leads to lowboiling, low viscosity, low value products such as short chainhydrocarbons, e.g. C₁-to C₄ hydrocarbons.

[0004] Hydrogen has always been used in catalytic dewaxing mainly forpromoting extended catalytic life by, e.g., reductive coke removal, seeU.S. Pat. No. 4,872,968. Hydrogen partial pressures in catalyticdewaxing ranges from about 200 psig (1480 kPa) to about 1,000 psig (6996kPa) or more, e.g., see U.S. Pat. No. 5,614,079, and hydrogen partialpressures are usually in the higher end of the range for reasons ofcatalyst life.

[0005] U.S. Pat. No. 5,362,378 discloses hydrogen partial pressuresranging from 72 to 2,305 psig (598 to 15994 kPa) for use with the largepore catalyst zeolite beta. This patent does not mention catalyst lifeor TIR, i.e., temperature increase required, necessary for maintainingproduct specifications, such as pour point or cloud point. Large porezeolite beta is typically not classified as a dewaxing catalyst, but asan isomerization catalyst, and products produced utilizing suchcatalysts in accordance with U.S. Pat. No. 5,362,378 would need to bedewaxed in order to achieve the low pour and cloud points obtained fromthe instant process.

[0006] It was the object of the present invention to provide for aprocess that will increase the yield of product with high boiling point,but low pour and cloud point. In other words, the process should havelittle or no hydrocracking. In particular, there is always a need for aprocess that will produce lube oils with high boiling point, highviscosity, and low pour and cloud points.

[0007] We have now found that a particular combination of featuresallows for conducting catalytic dewaxing in the substantial absence ofadded hydrogen, at low or no hydrogen partial pressure, and conditionsthat are selective to hydroisomerization with little or nohydrocracking. Surprisingly, the process of the invention allows for thedecrease of the pour or cloud points of a feed, while maintaining thehigh (kinematic) viscosity, and all of this with a high yield.

SUMMARY OF THE INVENTION

[0008] The invention relates to a catalytic dewaxing process whichcomprises reacting a paraffin containing feed stock over a catalystcomprising a molecular sieve with a one dimensional pore structurehaving an average diameter of 0.50 to 0.65 nm, and a metaldehydrogenation component, at dewaxing reaction conditions and in thesubstantial absence of added hydrogen.

[0009] In a preferred embodiment of this invention, a paraffincontaining feed, preferably a feed containing at least 80 wt %n-paraffins, is catalytically dewaxed in the presence of a molecularsieve catalyst with one dimensional pore structures having an averagediameter of 0.50 nm to 0.65 nm, and the difference between the maximumdiameter and the minimum diameter is preferably ≦0.05 nm. The molecularsieve is exemplified by, for example, ZSM-23, ZSM-35, ZSM-48, ZSM-22,SSZ-32, zeolite beta, mordenite and rare earth ion exchanged ferrieritein conjunction with a dehydrogenation component. Preferably themolecular sieve catalyst is ZSM-48 (ZSM-48 zeolites herein include EU-2,EU-11 and ZBM 30 which are structurally equivalent to ZSM-48) with adehydrogenation component; and the process is carried out in thesubstantial absence of added hydrogen.

[0010] By substantial absence of added hydrogen is meant the only addedhydrogen will be that which is inherently present in the feeds. In apreferred embodiment, the amount of inherent hydrogen in the paraffincontaining feed is the amount that is present in a Fischer Tropschhydrocarbon fraction. Such fraction is usually obtained by distillation,which distillation substantially removes dissolved gasses, and theamount of inherent hydrogen in the paraffin containing feeds is then theamount which is physically adsorbed by the liquid or waxy FischerTropsch hydrocarbon fraction.

[0011] When hydrogen is present during the reaction, either as aconsequence of the reaction or as inherent hydrogen, the hydrogenpartial pressure is preferably less than 100 psig (791 kPa), morepreferably less than 70 psig (584 kPa).

[0012] In another embodiment of this invention, the catalyst is stable,that is, it can meet a predetermined pour point for at least two weeks.

[0013] In yet another embodiment of this invention, a cyclic process isprovided wherein catalytic dewaxing occurs in a first zone while in asecond zone catalyst is regenerated or rejuvenated, after which the feedis switched to the second zone where catalyst has been regenerated andthe catalyst in the first zone is regenerated. Thus, a continuouscatalytic dewaxing process may be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a schematic of a cyclic isomerization-catalystregeneration process.

[0015]FIG. 2 is a plot showing the effect of hydrogen pressure on lubeyield for isomerization of a Fischer-Tropsch wax over Pt/ZSM-48. Pourpoint (° C.) is on the abscissa and wt % on feed 700° F.+ (371.1° C.+)lube yield is on the ordinate. The lines A, B, C, and D denote theresults of processes that were run with varying amounts of addedhydrogen, i.e. hydrogen partial pressures of 1000 psig (6996 kPa), 500psig (3549 kPa), 300 psig (2170 kPa), and 0 psia (0 kPa, no (added)hydrogen), respectively.

[0016]FIG. 3 is a plot showing the effect of hydrogen pressure on gasyield for isomerizing a Fischer-Tropsch wax over Pt/ZSM-48. 700° F.+(371.1° C.+) lube pour point (° C.) is on the abscissa and is plottedagainst wt % on feed C₁-C₄ gas yield on the ordinate. Lines A, B, C, andD denote the results of processes that were run with varying amounts ofadded hydrogen, i.e. hydrogen partial pressures of 1000 psig (6996 kPa),500 psig (3549 kPa), 300 psig (2170 kPa), and 0 psia (0 kPa, no (added)hydrogen), respectively.

[0017]FIG. 4 is a plot showing the effect of hydrogen pressure on lubeviscosity for isomerization of a Fischer-Tropsch wax over Pt/ZSM-48.Pour point (° C.) on the abscissa is plotted against kinematic viscosity@ 100° C. in centistokes (cSt) on the ordinate. Lines A, B, and C denote0 psia, 500 psig (3549 kPa), and 1000 psig (6996 kPa), respectively.

[0018]FIG. 5 is a plot showing the effect of hydrogen pressure on lubeviscosity index for isomerization of a Fischer-Tropsch wax overPt/ZSM-48. Pour point (° C.) on the abscissa is plotted against 700° F.+(371.1° C.+) lube viscosity index (VI) on the ordinate. The dotsrepresent 1000 psig (6996 kPa) hydrogen, the x's represent 500 psighydrogen (3549 kPa), the filled triangles represent 300 psig (2170 kPa)hydrogen, and the open diamond represents 0 psia hydrogen (0 kPa, nohydrogen).

[0019] For the particular set of features described herein, working inthe substantial absence of added hydrogen and at reduced hydrogenpartial pressures results in increased catalyst activity and increasedyield of desired product with little hydrocracking (as evidenced by thelow C₁-C₄ gas yields in FIG. 3).

DETAILED DESCRIPTION OF THE INVENTION

[0020] In FIG. 1, line 10 indicates a source of paraffin feed. Mostpreferably the feed is derived from a Fischer-Tropsch hydrocarbonsynthesis process, particularly one that is operated in a non-shiftingmode with a cobalt or ruthenium based catalyst, preferably a cobaltcontaining catalyst.

[0021] The feed is forwarded to first catalytic dewaxing zone 16 viaopen valve 12 and line 13. Hydrogen, to the extent desired, is fedthrough line 25. At the same time a source of an oxygen containing gas,i.e., oxygen, air, oxygen enriched air or oxygen in suitable proportionwith inerts such as nitrogen, from source 30, is fed to a second zone 18via open valve 32 and line 34 where deactivated catalytic dewaxingcatalyst is regenerated. Regeneration off gases are removed through openvalve 24 and line 26.

[0022] The catalytically dewaxed product from zone 16 is removed viaopen valve 44 through lines 40 and 48 to distillation zone 50 whereproducts are recovered, e.g., diesel in line 52 and lube base stock inline 54.

[0023] Upon deactivation of the catalyst in zone 16, valves 12 and 44are closed, oxygen from source 30 is fed to zone 16 via open valve 38and line 36. Regeneration off gases are removed through open valve 20and line 22.

[0024] Similarly, when zone 16 is being regenerated, valve 12 is closedand paraffin feed is delivered to zone 18 for catalytic dewaxing viaopen valve 14 and line 15. Hydrogen to the extent desired is fed throughline 27. Product is recovered in line 42 and fed via open valve 46 andline 48 to distillation zone 50.

[0025] The cyclic nature of the process is denoted by open valves 12,44, 32, and 24 and closed valves 14, 46, 38 and 20, and then upondeactivation of catalytic zone 16 with open valves 14, 46, 38, and 20and closed valves 12, 44, 32, 24, whereupon catalytic dewaxing takesplace in zone 18 and the catalyst in zone 16 is regenerated.

[0026] Catalytic dewaxing of paraffin containing feeds, preferably feedsproduced from syn gas using a non-shifting Fischer-Tropsch catalyst, isaccomplished at relatively low hydrogen partial pressures withoutsubstantial effect on the life of a ZSM-48 catalyst. The dewaxingprocess is essentially an isomerization process in which some hydrogenwill be produced indigenously.

[0027] The feed that is employed in this invention is a paraffincontaining feed, preferably a feed that contains greater than 80 wt %n-paraffins, more preferably greater than 90 wt % n-paraffins, stillmore preferably greater than 95 wt % n-paraffins and still morepreferably 98 wt % n-paraffins. The feed generally boils in the range430° F.+ (221.1° C.+), preferably 450° F.+ (232.2° C.+), more preferably450-1200° F. (232.2-648.9° C.) (minor amounts, e.g., less than about 10%of 1200° F.+, or 648.9° C.+, material may be present).

[0028] The feed is preferably low in unsaturates, that is, low in botharomatics and olefins. Preferably, the unsaturates level is less than 10wt %, preferably less than 5 wt %, more preferably less than 2 wt %.Also, the feed is relatively low in nitrogen and sulfur, e.g., less than200 ppm, preferably less than 100 ppm, such as less than 50 wppm ofeach. Where a Fischer-Tropsch derived feed is employed, there is no needto pre-sulfide the catalyst, and indeed, pre-sulfiding should beavoided.

[0029] Most preferably, the feed is the product of a Fischer-Tropschreaction that produces essentially n-paraffins, and still morepreferably the Fischer-Tropsch process is conducted with a non-shiftingcatalyst, e.g., cobalt or ruthenium, preferably a cobalt containingcatalyst.

[0030] The catalyst employed in the catalytic dewaxing step comprises amolecular sieve with one dimensional pore structure and a metaldehydrogenation component. The molecular sieves include such as ZSM-23,ZSM-35, ZSM-22, SSZ-32, zeolite beta, mordenite and rare earth ionexchanged ferrierite, preferably a ZSM-48 catalyst, containing a metaldehydrogenation functionality, preferably supplied by the presence ofplatinum or palladium or both platinum and palladium, more preferablyplatinum. The catalyst may be sulfided or unsulfided and is preferablyunsulfided when sulfur can negatively interfere with associatedprocesses, such as a Fischer-Tropsch process.

[0031] The molecular sieve catalyst support is described in J.Schlenker, et al., Zeolites, 1985, vol. 5, November, 355-358, herebyincorporated by reference. ZSM-48, in particular, is characterized bythe X-ray diffraction pattern shown in Table 1 below. The material isfurther characterized by the fact that it exhibits a single line withinthe range of 11.8±0.2 Angstrom units, i.e. (11.8±0.2)×10⁻¹⁰ m. Thepresence of a single line at the indicated spacing structurallydistinguishes ZSM-48 from closely related materials such as ZSM-12(described in U.S. Pat. No. 3,832,449) which has two lines, i.e., adoublet, at 11.8±0.2 Angstrom units, (11.8±0.2)×10⁻¹⁰ m, and high silicaZSM-12 (described in U.S. Pat. No. 4,104,294) which also has a doubletat the indicated spacing. TABLE 1 Characteristic lines of ZSM-48(calcined, Na Exchanged Form) Relative Intensity d(A, 10⁻¹⁰ m) (I/I_(O))11.8 ± 0.2  S 10.2 ± 0.2  W-M 7.2 ± 0.15 W 4.2 ± 0.08 VS 3.9 ± 0.08 VS3.6 ± 0.06 W 3.1 ± 0.05 W 2.85 ± 0.05  W

[0032] The values were determined by standard technique, i.e., radiationwas K-alpha doublet of copper, and diffractometer equipped with ascintillation counter. The peak heights, I, and the positions as afunction of two times theta, where theta is the Bragg angle, weredetermined by a compactor. From these the relative intensities, 100I/I_(O), where Io is the intensity of the strongest line or peak, andd(obs.), the interplanar spacing in A corresponding to the recordedlines were calculated. Table 1 gives the intensities in terms of thesymbols W=weak, S=strong, VS=very strong, M=medium, and W-M=weak tomedium (depending on the cationic form). Ion exchange of the sodium ionwith other cations reveals substantially the same pattern with someminor shifts in interplanar spacing and variation in relative intensity.Other minor variations can occur depending on the silicon to aluminumratio of the particular sample, as well as any subsequent thermaltreatment.

[0033] ZSM-48 and methods for its preparation are described in U.S. Pat.Nos. 4,375,573; 4,397,827; 4,448,675; 4,423,021; and 5,075,269. Themethod of preparation described in U.S. Pat. No. 5,075,269 isparticularly preferred, and is incorporated herein by reference. Thismethod is for preparing a catalyst particularly suitable for thecatalytic dewaxing process.

[0034] The zeolite, ZSM-48, and other utilizable zeolites, such asZSM-23, ZSM-35, ZSM-22, SSZ-32, zeolite beta, mordenite and rare earthion exchanged ferrierite, are usually employed with a dehydrogenationcomponent in an amount of about 0.01 to 5.0 wt %, the component beingmanganese, tungsten, vanadium, zinc, chromium, molybdenum, rhenium,Group VIII metals such as nickel, cobalt, or the noble metals platinumand palladium. The noble metals are preferred components. Such componentcan be exchanged into the composition, impregnated thereon, orphysically intimately admixed therewith. Such component can beimpregnated in or onto the zeolite such as, for example, in the case ofplatinum, by treating the zeolite with a platinum metal-containing ion.Thus, suitable platinum compounds include chloroplatinic acid, platinouschloride and various compounds containing the platinum tetra-ammoniacomplex. Platinum and palladium are preferred hydrogenation components.

[0035] The compounds of the useful platinum or other metals can bedivided into compounds in which the metal is present in the cation ofthe compound and compounds in which it is present in the anion of thecompound. Both types of compounds which contain the metal in the ionicstate can be used. A solution in which platinum metals are in the formof a cation or cationic complex, e.g., Pt(NH₃)₄Cl₂, is particularlyuseful.

[0036] Prior to its use, the ZSM-48 catalyst should be dehydrated atleast partially. This can be done by heating to a temperature in therange of from about 100° C. to about 600° C. in an inert atmosphere,such as air, nitrogen, etc., and at atmospheric or subatmosphericpressures for between 1 and 48 hours. Dehydration can also be performedat lower temperature merely by placing the catalyst in a vacuum, but alonger time is required to obtain sufficient amount of dehydration.ZSM-48 is formed in a wide variety of particle sizes. Generallyspeaking, the particles can be in the form of a powder, a granule, or amolded product, such as extrudate having a particle size sufficient topass through a 2 mesh (Tyler) screen (10 mm pore size) and be retainedon a 400 mesh (Tyler) screen (0.038 mm pore size). In cases where thecatalyst is molded, such as by extrusion, the crystalline silicate canbe extruded before drying, or dried or partially dried and thenextruded.

[0037] As in the case of many other zeolite catalysts, it may be desiredto incorporate the ZSM-48 with a matrix material which is resistant tothe temperatures and other conditions employed in the dewaxing processherein. Such matrix materials include active and inactive materials andsynthetic or naturally occurring zeolites as well as inorganic materialssuch as clays, silica and/or metal oxides, e.g. alumina. The latter maybe either naturally occurring or in the form of gelatinous precipitates,sols or gels including mixtures of silica and metal oxides. Use of amaterial in conjunction with the ZSM-48, i.e., combined therewith, whichis active, may enhance the conversion and/or selectivity of the catalystherein. Inactive materials suitably serve as diluents to control theamount of conversion in a given process so that products can be obtainedeconomically and orderly without employing other means for controllingthe rate of reaction. Frequently, crystalline silicate materials havebeen incorporated into naturally occurring clays, e.g., bentonite andkaolin. These materials, i.e., clays, oxides, etc., function, in part,as binders for the catalyst. It is desirable to provide a catalysthaving good crush strength since in a petroleum refinery the catalyst isoften subject to rough handling which tends to break the catalyst downinto powder-like materials which cause problems in processing.

[0038] Naturally occurring clays which can be composited with ZSM-48include the montmorillonite and kaolin families which include thesub-bentonites, and the kaolins commonly known as Dixie, McNamee,Georgia and Florida clays, or others in which the main mineralconstituent is halloysite, kaolinite, dickite, nacrite or anauxite. Suchclays can be used in the raw state as originally mined or initiallysubjected to calcination, acid treatment or chemical modification.

[0039] In addition to the foregoing materials, ZSM-48 can be compositedwith a porous matrix material such as silica-alumina, silica-magnesia,silica-zirconia, silica-thoria, silica-beryllia, silica-titania, as wellas ternary compositions such as silica-alumina-thoria,silica-alumina-zirconia, silica-alumina-magnesia andsilica-magnesia-zirconia. The matrix can be in the form of a cogel.Mixtures of these components can also be used. The relative proportionsof finely divided crystalline silicate ZSM-48 and inorganic oxide gelmatrix vary widely with the crystalline silicate content ranging fromabout 1 to about 90 percent by weight, and more usually in the range ofabout 2 to about 80 percent by weight, of the composite.

[0040] In general, reaction conditions for dewaxing may vary widely evenwhen the hydrogen partial pressures are maintained at low levels, e.g.,0 psig hydrogen. Thus, start of run temperatures may vary between about550°-650° F. (288°-343° C.). End of run conditions can be defined by thenature of the product being produced, for example, when colorspecifications can no longer be met (an indication of catalystdeactivation), or when the pre-determined pour point can no longer beobtained, or the selectivity to isomerization is reduced as evidenced byan increase in methane yield due to hydrocracking. In general, however,end of run temperatures should be less than about 800° F. (427° C.),preferably less than about 750° F. (399° C.), more preferably less thanabout 725° F. (385° C.).

[0041] Catalyst deactivation is believed to be a result of cokeformation on the surface of the catalyst, the coke covering or blockingaccess to the catalytic metal, as well as blocking the pores of thezeolite.

[0042] The catalyst may be regenerated by known methods including hothydrogen stripping, coke removal by oxygen treatment or a combination ofhydrogen stripping and oxygen treatment. (FIG. 1 illustrates a processwhere oxygen treatment is used to regenerate the catalyst).

[0043] Briefly, hydrogen stripping can be carried out with hydrogen or amixture of hydrogen and an inert gas such as nitrogen, at isomerizationreaction temperatures for a period of time sufficient to allow thecatalyst to regain at least about 80%, preferably at least about 90% ofits original lined out activity. Oxygen treatment can be carried out atcalcining conditions, e.g., using air at temperatures from about 500° C.to 650° C., again for a period of time sufficient to allow the catalystto regain at least about 80%, preferably at least about 90% of initiallined out activity after subsequent reduction.

[0044] In general, where hydrogen is present, other gases may bepresent, too, and will not interfere with the reaction. Such other gasesmay be nitrogen, methane, or other light hydrocarbons (that may beproduced during the reaction). Total pressure may range up to 2000 psia(13790 kPa), preferably 100-2000 psia (690-13790 kPa), more preferably150-1000 psia (1034-6895 kPa), still more preferably 150-500 psia(1034-3448 kPa). Hydrogen can make up 50-100% of total gas, preferably70-100%, more preferably 70-90%. At the low hydrogen partial pressuresrecited herein, small amounts of olefins and aromatics may form when theisomerization is carried out in the substantial absence of hydrogen; andhydrofinishing, at well known conditions, may be necessary to removethese components.

[0045] The liquid hourly space velocity is generally between about 0.1and about 10, and preferably is generally between about 0.5 and 4 volumeof feed per volume of catalyst per hour. The hydrogen to feed (wherehydrogen is used) ratio is generally between about 100 (17.8liter/liter) and about 10,000 (1781 liter/liter), and preferably betweenabout 800 (142.5 liter/liter) and about 4,000 (712.4 liter/liter)standard cubic feet (scf) of hydrogen per barrel of fuel.

[0046] Alpha Value is an approximate indication of the catalyticcracking activity of the catalyst compared to a standard catalyst andprovides a relative rate constant (rate of normal hexane conversion pervolume of catalyst per unit time). The value is based on the activity ofa silica-alumina cracking catalyst taken as an Alpha of 1 (rateconstant=0.016 sec⁻¹). The test for Alpha Value is described in U.S.Pat. No. 3,354,078 and in the Journal of Catalysis. vol. 4, p. 527(1965); vol. 6, p. 278 (1966); and vol. 61, 395 (1980), eachincorporated herein by reference. The Alpha Value of the catalyst priorto metal loading is preferably in the range of about 10 to about 50.

[0047] In the following examples, a Fischer-Tropsch wax having theproperties shown in Table 2 below was used as feedstock for allisomerization reactions. TABLE 2 Fischer-Tropsch Wax Pour point, °C. 82IBP-700° F. (371.1° C.) (<C₂₄), wt % 3 700° F. (371.1° C.) − 1100° F.(593.3° C.) (C₂₄-C₆₀), 89 1100° F. + (593.3° C.+) (C₆₀+), wt % 8

[0048] In all examples the catalyst was alumina bound (35 wt %), ZSM-48crystals containing 0.6 wt % platinum (Pt dispersion based on hydrogenabsorption: H/Pt=1.03).

[0049] Wax isomerization was performed using a micro unit equipped witha three zone furnace and a downflow trickle bed tubular reactor (0.5inch ID). The unit was heat traced to avoid freezing of the high meltingpoint feed wax. The catalyst extrudates were crushed and sized to 60-80mesh (0.180-0.250 mm). The reactor was loaded with a mixture of 15 ccsized catalyst and 5 cc of 80-120 mesh (0.125-0.180 mm) sand, which wasthen dried and reduced at 400° F. (204.4° C.) for one hour at oneatmosphere, 240 cc/min hydrogen flow. Isomerization was conducted at 1.0hr⁻¹ LHSV and at pressures indicated. When hydrogen was used as aco-feed, the hydrogen/feed ratio was 5000 scf/bbl (890.5 liter/liter).In cases where no hydrogen was used, reactor pressure was maintained at1000 psig (6996 kPa). Isomerization reactions were started with feed atan initial temperature of 665° F. (351.7° C.) and hydrogen (where used)as noted. Material balances were carried out overnight for 16-24 hoursafter 8-12 hour line out period. Reactor temperature was graduallychanged to vary pour point.

[0050] Off gas samples were analyzed by GC using a 60 m DB-1 (0.25 mmID) capillary column with FID detection. Total liquid products (TLP's)were weighed and analyzed by simulated distillation (M1567 or D2887).TLP's were distilled into IBP-330° F. (initial boiling point-165.6° C.)naphtha, 330-700° F. (165.6-371.1° C.) distillate, and 700° F.+ (371.1°C.+) lube fractions. The lube fractions were analyzed further bysimulated distillation (simdis) to ensure accuracy of the actualdistillation operations. Pour point and cloud point of 700° F.+ (371.1°C.) lubes were measured using D97 and D2500 methods, respectively;viscosities were determined at both 40° C. and 100° C. according to D445-3 and D 445-5 methods, respectively.

[0051] Hydrogen pressure was found to affect substantially both catalystactivity and product selectivity. Upon decreasing hydrogen pressure,catalyst activity increased, e.g., 25-30° F. (14-16.7° C.) wherehydrogen pressure was reduced from 1000 psig (6996 kPa) to 300 psig(2170 kPa). Similarly, selectivity to lube base stock (700° F.+, 371.1°C.+) increased with decreasing hydrogen pressure. FIG. 2 shows that lubeyield was higher at lower hydrogen pressure. A maximum lube yield (app.90% at −12° C. pour point) was obtained in the substantial absence ofadded hydrogen. At the same time, the yields of lighter by-products,that is, light gas (C₁-C₄), naphtha, and distillate were decreased withdecreasing hydrogen pressure. Thus, the increased lube yield is clearlya function of increased selectivity for the catalyst.

[0052] By virtue of the enhanced selectivity, there appears to be lowerrates of cracking side reactions. As hydrogen pressure is reduced,catalyst activity increases and a lower reaction temperature is requiredto achieve a target, or pre-determined, lube pour point. Both factors,substantial absence of hydrogen and lower reaction temperature shouldreduce cracking, such as hydrogenolysis and thermal or catalyticcracking. Hydrogenolysis in the absence of hydrogen should benegligible. See FIG. 3 regarding gas yields.

[0053] Lube base stock viscosity at a given, or pre-determined, pourpoint was higher, too, at lower hydrogen pressure, and reached a maximumwith no hydrogen as co-feed; i.e., 0 kPa (zero psia) hydrogen. Forexample, at −20° C. pour point, the 700° F.+ (371.1° C.+) lube basestock obtained without co-feeding hydrogen had a KV at 100° C. of 7.7cSt which is significantly higher than the 6.7 cSt base stock obtainedwith a 1000 psig (6996 kPa) hydrogen pressure, as shown in FIG. 4.Hence, it is especially surprising that, using the process of theinvention, the viscosity of the feed is better preserved, while at thesame time the pour and cloud point is decreased.

[0054] Viscosity and viscosity index are two key properties of lube basestocks. FIG. 5 shows that lowering hydrogen partial pressure, even to 0psia (0 kPa), essentially had no effect on viscosity index of the lubebase stocks.

[0055] Table 3 below shows the results of isomerizing a Fischer-Tropschwax, i.e., catalytic dewaxing in the substantial absence of addedhydrogen. “MB” refers to material balance. TBP x% indicates a finalboiling temperature, at which x wt % light fraction of a hydrocarbonsample boils. TABLE 3 MB Number 1 2 3 4 Time on Stream, Days 62.5 64.565.6 66.6 Temperature, ° F. 630 625 620 620 Temperature, ° C. 332.2329.4 326.7 326.7 Pressure, psig 1000 1000 1000 1000 Pressure, kPa 69966996 6996 6996 LHSV, hr⁻¹ 1.0 1.0 1.0 1.0 WHSV, hr⁻¹ 2.3 2.2 2.2 2.2 H₂@ inlet, scf/bbl 0 0 0 0 H₂, Hydrocarbon Feed, l/l 0 0 0 0 ProductYield, wt % Feed C₁-C₄ Gas, wt % 2.8 1.2 0.6 0.4 C₅-330° F. Naphtha. wt% 7.5 3.9 1.4 0.4 330-700° F. Diesel, wt % 18.0 12.0 8.0 6.0 700° F. +Lube Yield, wt % 72.0 83.0 90.0 93.2 Total HC, wt % on Feed 100.3 100.1100.1 100.0 Lube Properties Isolated Yield, wt % 70.8 82.3 86.0 88.4 KV@ 40° C., cSt 40.1 38.7 40.6 41.4 KV @ 100° C., cSt 7.39 7.44 7.85 8.10Viscosity Index 152.1 162.1 168 173.5 Pour Point, ° C. D97 −42 −33 −12 3TBP 5%, ° F. by D2887 770 779 798 838 TBP 5%, ° C. by D2887 410.0 415.0425.6 447.8 TBP 50%, ° F. 913 924 923 947 TBP 50%, ° C. 489.4 495.6495.0 508.3 TBP 95%, ° F. 1044 1050 1042 1070 TBP 95%, ° C. 562.2 565.6561.1 576.7 MB Closure, wt % 100.0 100.0 100.0 100.2

What is claimed is:
 1. A catalytic dewaxing process which comprisesreacting a paraffin containing feed stock over a catalyst comprising amolecular sieve with a one dimensional pore structure having an averagediameter of 0.50 to 0.65 nm, and a metal dehydrogenation component, atdewaxing reaction conditions and in the substantial absence of addedhydrogen.
 2. The process of claim 1 wherein the catalyst deactivationrate, as measured by temperature increase required to meet apredetermined pour or cloud point (TIR) is less than 25° F./year (14°C./year).
 3. The process of claim 1 wherein the hydrogen partialpressure is less than about 100 psig (791 kPa).
 4. The process of claim3 wherein the hydrogen partial pressure is less than about 70 psig (584kPa).
 5. The process of claim 4 wherein the paraffin containing feedstock contains greater than 80 wt % n-paraffins and boils in the rangeabove 430° F. (221.1° C.).
 6. The process of claim 5 wherein thedehydrogenation component is platinum or palladium.
 7. The process ofclaim 6 wherein the process comprises a cyclic catalyticdewaxing-catalyst regeneration process wherein catalyst is provided in afirst reaction zone and a second reaction zone, the paraffin containingfeed stock is dewaxed in the first reaction zone for a pre-determinedperiod after which the paraffin containing feed is transferred to thesecond zone for dewaxing at reaction conditions, and catalyst in thefirst zone is regenerated.
 8. The process of claim 7 wherein dewaxingoccurs in the second zone for a pre-determined period after which theparaffin containing feed is transferred to the first reaction zonewherein dewaxing occurs over the regenerated catalyst, and the catalystin the second zone is regenerated.
 9. The process of claim 8 whereincatalyst regeneration is effected by hydrogen stripping or oxygentreatment.
 10. The process of claim 5 wherein the product of thecatalytic dewaxing process is a lube base stock or a diesel rangematerial.
 11. The process of claim 10 wherein the product is subjectedto hydrofinishing.
 12. The process of claim 11 wherein the molecularsieve is selected from the group consisting of ZSM-23, ZSM-35, ZSM-48,ZSM-22, SSZ-32, zeolite beta, mordenite, rare earth ion exchangedferrierite and mixtures thereof.
 13. The process of claim 12 wherein themolecular sieve is ZSM-48.
 14. Use of the process according to claim 13to (1) decrease the pour point or cloud point, or both, and (2) preservethe viscosity of a paraffin containing feed stock.